It seems I was not the first one experiencing the crash ([1], in German).

Quick'n'dirty Fix

As I have just a rough idea how the LA coding works I tried several changes to some files, but finally only sledgehammer tactics worked. In <LA_Dir>/gamedata/config/misc/trade_killer2.ltx I deleted line 3:

Not sure what side effects this will have (wild guess: Milo will no longer sell to me), so I will definitely remove the fix before the next new game. But for the time being I am able to enter Dead City and hunt for Borzij.